Second-generation polyolefin production processes (e.g., bulk and vapor phase polypropene) are economically attractive when polymer yields are high enough and solubles (hexane extractables) are low enough to make catalyst residues and solubles removed unnecessary. The presence of catalyst residues in the polymer product results in a relatively high chlorine compound content in the product. Thus, for example, the polypropene from a 4000 lbs/lb titanium trichloride polymerization process, prepared by a catalyst consisting of diethylaluminum chloride and active titanium trichloride in about a 3:1 molar ratio, can contain above about 300 ppm of chlorine as chloride. This chloride, which is present in the form of metal chlorides, is hydrolyzed during the catalyst deactivation step or steps to yield hydrogen chloride. The latter can cause degradation of the polymer product during extrusion, molding, etc., if not properly neutralized. There are several conventional methods of neutralizing the hydrogen chloride in the polymer, e.g., addition of calcium hydroxide leads to the formation of calcium chloride while addition of propene oxide results in the formation of propene and chlorohydrins. In the former case the chlorine remains in the polymer in the form of calcium chloride, whereas in the latter case a fraction of the chloride is removed during drying or storage of the powder (the b.p. of propene chlorohydrins is 125.degree.-130.degree.C).
Now we have found compounds superior in their effectiveness for chlorine removal, the residual effects of which compounds are negligible on the polyolefin when the dechlorinated polymer is being processed.